Has anyone used cassette tape adapter's "tape head" in a tape echo?

[jatalahd]

It seems that it is impossible to buy new tape heads these days and I don't want to start collecting old cassette players only to get a few parts out of them. Then I found out that these kind of cassette tape adapters are still widely available:

https://en.wikipedia.org/wiki/Cassette_tape_adapter

They seem to have a "tape head" that couples directly to the tape head of a cassette player, but I am not sure if the adapter's head has the same characteristics as a "standard" tape head found from cassette players. The plan is obviously to get 3 of those and use one for reading, one for writing and one for erasing a cassette tape. Could these work in a tape echo?

Any experiences or thoughts regarding this topic are highly appreciated.

[anotherjim]

In principle yes.
But...
Those adapters don't need to pass tape, so I don't know if the head will without shredding the tape! I've never actually seen one - it would be neat if they are a stock cassette head.
Aren't erase heads usually a lower impedance to get more power into the erase field? Although that doesn't mean you can't make any play/record head do the job.

[PRR]

A tape head has a very small active "gap" for good high frequency response.

To *induce* audio in such a head, it is convenient to use a "large" field so the alignment does not have to be exact.

But these adapters are very-very cheap now. Get one or two and try it.

[merlinb]

[Axldeziak]

Standard cassette heads are also used in the credit card readers made for cell phones.

[jatalahd]

Those adapters don't need to pass tape, so I don't know if the head will without shredding the tape! I've never actually seen one - it would be neat if they are a stock cassette head.
Aren't erase heads usually a lower impedance to get more power into the erase field? Although that doesn't mean you can't make any play/record head do the job.

Good points, at least those adapter heads seem to be missing the tape "guides" that are supposed to keep the tape aligned with the head. In sophisticated tape recorders, the play, record and erase heads have different characteristics so using same head type for all three is a huge compromise. The question is, is the quality still enough for an echo effect. Or it might produce some interesting Lo-Fi effect in any case.

Standard cassette heads are also used in the credit card readers made for cell phones.

This is interesting! I googled a bit and somewhere it said that these readers were given out for free at some point in time...

But these adapters are very-very cheap now. Get one or two and try it.

Yes, they are cheap. I ordered 10 of these, although I have not yet received a confirmation on delivery... (maybe I exceeded their stock).

Well, based on this, it seems that no one has tried to use these adapter heads with a real cassette tape to play and record audio. If I get my order delivered to me, I will test those and see what comes out. The patent application for the adapter stated that the head would be in fact a record head so I will start by trying to record audio on a pre-erased tape and then play the recording back with a "normal" cassette player. The problems I need to overcome are to come up with a suitable bias signal frequency (100 kHz?), signal strength and tape alignment so that the recording avoids most of the distortion and stays in correct track. Some kind of test bench I need to build for this I guess.

While searching for information I stumbled across this excellent book:
http://www.tubebooks.org/Books/Burstein_tape.pdf

And tape head specification documents (scroll to the bottom part of the page for pdf-files):
http://www.jrfmagnetics.com/index.html?JRF_mainframe=/JRF_nortronics.html

And lastly I have to admit being wrong about not able to buy "new" heads:
https://www.surplussales.com/Equipment/magnetic-tape.html

These are most likely from an old stock of Nortronics that JRF bought, I am not sure if Nortronics still manufactures new tape heads. If someone has more info on this, please let me know.

[Strategy]

This is sort of a sidebar to this discussion but if you are into messing with tape heads, look at Nicolas Collins' fun DIY book "Handmade Electronic Music" has at least one fun tape head project. Also a project that uses credit card swiping technology in a similar application (magnetic reader modded for noise making)
- Strategy

[jatalahd]

This is sort of a sidebar to this discussion but if you are into messing with tape heads, look at Nicolas Collins' fun DIY book "Handmade Electronic Music" has at least one fun tape head project. Also a project that uses credit card swiping technology in a similar application (magnetic reader modded for noise making)
- Strategy

Thanks! And guess what, I bought that specific book a few years ago but had no time then to read it thoroughly. So thanks to you, I am reading it now  while typing this

[jatalahd]

For future reference and for other interested, I found (what at least seems to be) a perfect resource of information about electric circuits used to make a decent cassette recorder/player:

https://www.keith-snook.info/wireless-world-magazine/Wireless-World-1976/Low-noise%20low-cost%20cassette%20deck.pdf

Among other things, it shows that a simple textbook example of a Clapp oscillator with the tape head as the inductor can be used for creating a 50 kHz AC bias signal for erase and record heads with relatively low operating voltage of 12 volts. Also the required signal levels are discussed in detail. I am planning to try how it behaves at 9 volts. Also an example of playback signal amplification circuitry is shown and explained. The design is perfect in the sense that it can be built using parts from the nearest component dealer, without the need to hunt for customized audio transformers or other rarely used stuff.

[jatalahd]

So I was left with no choice but try this out myself. And I am so glad I did try it! Eventually I got a prototype working, although I was extremely skeptic about getting the tape heads aligned properly and the recording bias working. But at the end it was more easier than I thought.

So I built a bias oscillator, record amplifier and playback amplifier on my breadboard, took out a cassette deck mechanism from a dead cassette player and glued two tape adapter heads to a basic C-cassette. If someone is interested, I made a short video about how it sounds. Here I am only taking the wet signal to my loudspeaker, this was the first try I did on the system. I must say I did not expect to get it sounding that good... (of course the background noise is there, but noise seems to follow me in everything I do so nothing new here...). If you check out the video, do not listen on loud volume, the audio on the video is quite loud and there are a few snaps an pops at the start.

It seems that the heads in the tape adapters are standard combined rec/play heads commonly used in cheap cassette decks, so they are good for both playback and record. I got two different types of adapters and the heads in them all seem to have 100mH inductance and 250 ohms of resistance, stereo heads, but mono would be sufficient for guitar effect. I have ordered a third type of adapters for more investigations. I have not tested how to use the heads for erasing, but I think I don't need to erase. When using a C90 cassette, I have 45 minutes to use the echo effect and then I can just record empty on top afterwards. Then re-use in the echo effect... Here is a picture of the heads obtained from the cassette adapters:




And here is how I attached them to the cassette, the one in the left "hole" does the recording and the one in the middle does playback:



So I first glued some padding plastic to the inside of the cassette (equal amount on both sides), so that the head just and just fits in the middle of the padding. This ensures that the heads are aligned to the middle of the cassette and assumingly to the middle of the tape as well. When the padding was there, then I glued the heads between the paddings to make them stay firmly at place when testing. What surprised me the most was that I had no tape alignment "gates" whatsoever in the tape heads and still the recording and playback were nicely aligned on correct track (I used only one track, as in mono). I also took off the pressure pad that normally pushes the tape firmly to the tape head. Again, I was surprised that it is not needed at all when the tape heads are mounted deep enough in the cassette. The tape seems to tighten and align itself very well when the pinch roller of the deck mechanism is pulling the tape and the two tape heads are digging deep to the tape to add some friction to the system.

Here is the modified cassette placed on the deck mechanism, which is only needed for rolling the tape mainly using the pinch roller to keep a steady tape movement going on:



Here are the bits and pieces of the circuits I used to make it happen. I am happy that very simple circuits are enough for this:

I used a bias oscillator that was introduced in the book "Audio Electronics" by John Linsley Hood. With a 1mH radial coil having less than 5 ohms of series resistance, I get about 16 to 20 volts r.m.s. (about 50 volts peak to peak) sine wave at 50 kHz from a 9 volt battery! That is sufficient for biasing the record head for linear recording. It seems that the higher the bias voltage, the better recording I get.



As for the record amplifier I was not happy with the circuits I found online, so I made my own. Below it also shows the frequency response of the amplifier. It accentuates the high frequencies as it is typically instructed to do. And it seems to work well... It uses an off-the-self 1.5 mH radial coil to get a low-pass filter with a clear resonance peak just around 10 kHz.






And finally the playback amplifier. I used the low-noise pre-amp suggested by John Linsley Hood in the article that I previously posted the link.



Additionally I added a feedback loop from the output of the playback amplifier to the input of the recording amplifier. With that I can get the thing oscillating forever on a given note .... or at least to the point where the tape runs out

The cassette mechanism was powered from a separate power supply as the thing was still partially attached to the old radio I took apart. In the future I need to try and make it an integrated unit, where I can control the tape speed to get varying delay times.

I tried to post a reasonably comprehensive set of information here, just in case someone else is interested in experimenting with a tape echo effect.

[Marcos - Munky]

That's pretty interesting and it indeed sounds very good! I never played with tape heads, so I don't have a clue on how to wire them, but you did a great work. If you can add an erase head after the playback head, you can mod the tape to make a single loop that runs endlessly.

[anotherjim]

Awesome work! Thanks for posting. Usually, this kind of thing only gets thought/talked about!